It is a concern in the power tool industry to maximize battery life and to prevent battery damage. Further, it is desirable to maximize motor life and prevent motor damage. Typical cordless power tools use nickel cadmium (NiCd), nickel metal hydride (NiMH) or lithium ion batteries and draw 30 to 35 or more amps while under heavy load. Serious degradation of NiCd battery life occurs at or above 50 amps of current. While under heavy loads, near stall or when a battery is nearly depleted, the power tool may draw in excess of 50 amps. Other battery types have different tolerances for high current. For example, above 15 amps, damage associated with temperature may occur to state of the art lithium ion batteries.
Thus, it would be desirable to provide a circuit to limit current from a battery to a motor in a power tool.